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PROTOCOL.md

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The Fabric Protocol

Fabric implements a TCP-based networking protocol for establishing and executing peer-to-peer agreements.

Messages

Fabric Messages are hex-encoded bytestreams with a fixed-length header and an optional payload.

Fabric Message Format

The Fabric Message Format consists of two (2) components; the message header (the "Header") and the message body (the "Payload").

Fabric Message Header

  • magic — 4 bytes C0DEF33D (constant)
  • version — 4 bytes 00000001 (variable)
  • parent — 32 bytes (parent state identifier)
  • type — 4 bytes (message type)
  • size — 4 bytes (payload size)
  • checksum — 32 bytes (sha256sum of payload)
  • signature — 64 bytes (composable signature by message author of the checksum)

Fabric Message Payload

  • (optional) payload — size bytes

Types

The base list of Fabric Message Types is as follows:

  • GENERIC — decimal 128 (0000080)
  • STATE — decimal 192 (00000C0)
  • DELTA — decimal 193 (00000C1)
  • ACK — decimal 200 (00000C8) (may change)
  • LOCK — decimal 232 (00000E8)
  • ANNOUNCE — decimal 256 (0000100)
  • BID — decimal 300 (0000012C)
  • ASK — decimal 402 (0000192)
  • CLOSE — decimal 512 (0000200)

The GENERIC Message Type

UTF8-encoded JSON payload.

If the version field is 1 the payload MUST be valid JSON.

The ANNOUNCE Message Type

Used for Peer announcements.

The STATE Message Type

Pure State snapshots.

The DELTA Message Type

State delta in JSON-PATCH format.

The LOCK Message Type

Halt forward movement.

The ACK Message Type

Confirm receipt of a message.

The ASK Message Type

Ask for payment to unlock a specific document.

The BID Message Type

Offers a payment to unlock of specific document.

The CLOSE Message Type

Cancel a previous message.

Generic Messages

Generic messages use the GENERIC type and are currently implemented with UTF8 payloads.

Compute

Fabric provides a reference REPL (Read, Evaluate, Print, Loop) interface via the fabric command.

Fabric Compute Space

Certain generic types are provided within any Fabric Compute Space.

Actor

The Actor type maps an object to its unique identifier.

ActorSet

An ActorSet is a hashmap of Actor instances, address by their ID.

Collection

A Collection is a list of Actor instances.

Contract

The Contract class provides a simple method for creating agreements between a known set of peers.

Peering

Peers are identified in the Fabric network by their Fabric Identity, a bech32m encoding of the prefix id and public key body.

Connecting to other peers in Fabric requires knowledge of the peer's public key.

$ fabric
C^i
/connect 0375f7cfc3fa3bc9ed621019018fca678da404a29c8dfec4350855b5ad2f0a42d7@hub.fabric.pub:7777

Peer Protocol

Initiator sends a P2P_SESSION_OFFER message, counterparty responds with P2P_SESSION_OPEN message.

INITATIOR                     COUNTERPARTY
00: CONNECT
01: SESSION_OFFER ->
02:                               VALIDATE
03:                        <- SESSION_OPEN
04: READY

The Session is now open.

Negotiation

incorrect state            correct state
  |                                    |
  v                                    |
  prior state                          |
  |                                    |
  v                                    |
  timeout                              |
  |                                    |
  |                                    |
  |                                    v
   \---------------------------------> sign -> broadcast

Layers

sha256(input) -> sha256(hash) -> (100% signing set signature)